1. Field of the Invention
The present invention relates to cranks for bicycle pedals.
2. Description of the Prior Art
At the present time, these pedal cranks are manufactured in a single piece of metal and formed in particular of light metal alloy. However, the very fact that they are intended to transmit large forces makes it necessary to design pedal cranks having suitable dimensions. Under these conditions, although they are made of light metal alloy, they still have a relatively substantial weight which constitutes a disadvantage for the equipment of racing bicycles.
With a view to reducing the weight of bicycle frames, it has already been proposed to replace the metal tubes usually employed for the construction of frames by tubular elements fabricated from synthetic resin reinforced with textile fabric as disclosed in European Pat. No. 127,553. However, a solution of this type cannot be adopted for pedal cranks by reason of the particular problems raised by the need to mount a pivoting pedal on one end of a crank and a crankshaft or so-called bottom bracket spindle on the other end of the crank.
Moreover, French Pat. No. 417,313 describes a pedal crank constituted by a number of die-stamped parts suitably welded together instead of being formed of a single forged part. However, this solution does not permit any reduction in weight since the components of the corresponding crank are all of die-stamped sheet metal including the crank arms and these components are integrally assembled by welding.
For the reasons given in the foregoing, the aim of this invention is to produce a bicycle pedal crank so designed as to afford a degree of mechanical strength equivalent to that of current designs while being of much lower weight.